Engineering bacteria for production of rhamnolipid as an agent for enhanced oil recovery

Abstract

Rhamnolipid as a potent natural biosurfactant has a wide range of potential applications, including enhanced oil recovery (EOR), biodegradation, and bioremediation. Rhamnolipid is composed of rhamnose sugar molecule and beta-hydroxyalkanoic acid. The rhamnosyltransferase 1 complex (RhlAB) is the key enzyme responsible for transferring the rhamnose moiety to the beta-hydroxyalkanoic acid moiety to biosynthesize rhamnolipid. Through transposome-mediated chromosome integration, the RhlAB gene was inserted into the chromosome of the Pseudomonas aeruginosa PAO1-rhlA(-) and Escherichia coli BL21 (DE3), neither of which could produce rhamnolipid. After chromosome integration of the RhlAB gene, the constitute strains P. aeruginosa PEER02 and E. coli TnERAB did produce rhamnolipid. The HPLC/MS spectrum showed that the structure of purified rhamnolipid from P. aeruginosa PEER02 was similar to that from other P. aeruginosa strains, but with different percentage for each of the several congeners. The main congener (near 60%) of purified rhamnolipid from E. coli TnERAB was 3-(3-hydroxydecanoyloxy) decanoate (C(10)-C(10)) with mono-rhamnose. The surfactant performance of rhamnolipid was evaluated by measurement of interfacial tension (IFT) and oil recovery via sand-pack flooding tests. As expected, pH and salt concentration of the rhamnolipid solution significantly affected the IFT properties. With just 250 mg/L rhamnolipid (from P. aeruginosa PEER02 with soybean oil as substrate) in citrate-Na(2)HPO(4), pH 5, 2% NaCl, 42% of oil otherwise trapped was recovered from a sand pack. This result suggests rhamnolipid might be considered for EOR applications.

Root Exudation: The Ecological Driver of Hydrocarbon Rhizoremediation

“…Organic acid anions exuded by roots may also enhance the desorption of hydrocarbons and/or compete for soil adsorption sites from the soil matrix, such as clay surfaces [6,255,266]. Moreover, some microorganisms are able to release biosurfactants, such as rhamnolipids, that can increase the solubility of certain organic contaminants and improve the ability of microbial cells to attach to oil droplets [267][268][269].…”

Studies on the Effects of Bioprocess Parameters and Kinetics of Rhamnolipid Production by P. aeruginosa NITT 6L

“…The rhamnose concentration was calculated from standard curves prepared with L-rhamnose (0-100 mg L -1 ) using phenol-sulphuric acid method. 15 Effect of agitation on rhamnolipid production Effect of agitation was studied at three different agitation speeds 100, 150 and 200 rpm in 250 mL flasks containing 100 mL production media. These flasks were inoculated with 2 % overnight seed culture at an initial pH 7 and incubated at 37 °C for 72 h in rotary shaker.…”

Biosurfactant Production from n-Paraffins by an Air Isolate Pseudomonas aeruginosa OCD1

“…The biosurfactant was precipitated by acidifying culture supernatant to pH 2 with concentrated HCl and kept at 4 overnight, then recovered by centrifugation at 12,000 r.p.m for 1 h. The precipitate was dissolved in deionized water. Two volumes of chloroform and methanol 2:1, v/v were added to biosurfactant solution and shaken 30 min for extraction 17 . The organic phase was separated and evaporated to dryness using a rotary vacuum evaporator EYELA, Rikakikai Co. Ltd., Tokyo, Japan to give the crude biosurfactant at 45 .…”